3(2h)pyridazinone, process for its preparation and anti-allergic agent

Abstract

A 3(2H)pyridazinone of the formula: ##STR1## wherein R.sub.1 is hydrogen, methyl, C.sub.3 -C.sub.6 alkenyl, C.sub.5 or C.sub.6 cycloalkyl, benzyl, phenyl, --(CH.sub.2).sub.m CO.sub.2 R.sub.3 (wherein R.sub.3 is hydrogen or C.sub.1 -C.sub.5 alkyl, and m is an integer of from 1 to 4), --(CH.sub.2).sub.n A (wherein A is --OH or --N(R.sub.4).sub.2 wherein R.sub.4 is C.sub.1 -C.sub.3 alkyl, and n is an integer of from 2 to 6) or --CH.sub.2 CF.sub.3 ; R.sub.2 is chlorine or bromine; each of Y.sub.1 and Y.sub.2 which may be the same or different, is hydrogen, C.sub.1 -C.sub.5 alkyl, C.sub.2 -C.sub.8 alkenyl, halogen, --OR.sub.5 (wherein R.sub.5 is hydrogen, C.sub.1 -C.sub.8 alkyl or ##STR2## wherein q is an integer of from 1 to 4), --CO.sub.2 R.sub.6 (wherein R.sub.6 is hydrogen or C.sub.1 -C.sub.5 alkyl), --N(R.sub.7).sub.2 (wherein R.sub.7 is C.sub.1 -C.sub.4 alkyl) or --SR.sub.8 (wherein R.sub.8 is C.sub.1 -C.sub.4 alkyl); and Y.sub.3 is C.sub.1 -C.sub.5 alkyl, C.sub.2 -C.sub.8 alkenyl, halogen, --OR.sub.5 (wherein R.sub.5 is as defined above), --CO.sub.2 R.sub.6 (wherein R.sub.6 is as defined above), --N(R.sub.7).sub.2 (wherein R.sub.7 is as defined above) or --SR.sub.8 (wherein R.sub.8 is as defined above), or a pharmaceutically acceptable salt thereof.